SC.912.E.7.2: Analyze the causes of the various kinds of surface and deep water motion within the oceans and their impacts on the transfer of energy between the poles and the equator. SC.912.E.7.3: Differentiate and describe the various interactions among Earth systems, including: atmosphere, hydrosphere, cryosphere, geosphere, and biosphere. SC.912.E.7.4: Summarize the conditions that contribute to the climate of a geographic area, including the relationships to lakes and oceans.

SC.912.E.7.7: Identify, analyze, and relate the internal (Earth system) and external (astronomical) conditions that contribute to global climate change. SC.912.E.7.6: Relate the formation of severe weather to the various physical factors. SC.912.E.7.5: Predict future weather conditions based on present observations and conceptual models and recognize limitations and uncertainties of such predictions.

The three-cell model divides the circulation of each hemisphere into three distinct cells: the heat-driven Hadley cell that circulates air between the Tropics and subtropics, a Ferrel cell in the middle latitudes, and a polar cell.

Thermohaline Circulation in the Atlantic

Three astronomical factors influence the Climate cycles of glacial & interglacial periods: Eccentricity - Obliquity - Precession – These three factors make up the Milankovitch cycles.

The eccentricity of Earth’s orbit changes cyclically with a cycle of about 100,000 years being especially prominent.

Obliquity refers to the tilt of Earth’s axis, which also varies cyclically (Tilt varies between 22° and 25° off the perpendicular).

Precession (wobble) is the cyclical change in the orientation of Earth’s axis.

These astronomical forces, or Milankovitch Cycles, coincide and reinforce one another every 100,000 years. Over time, natural climate change involves 90,000 years of cooling, followed by 10,000 years of warming. These natural cycles result in glacials/interglacials.

The end of the last Ice Age was approximately 12,000 years ago. Sea level was 120 meters lower than today.

We should have “turned the corner” and entered into a gradual cooling phase.

Don’t changes in solar activity cause climate change? Yes and No! In the past, solar activity was a major climate forcing mechanism. Today, the rapid and abundant output of GHGs dwarfs the solar influence.

The solar constant is decreasing. Simultaneously, global temperatures have steadily increased.

Don’t volcanoes produce more CO 2 than humans? Volcanoes on land and under the sea release about 200 million tons of CO 2 annually. Fossil fuel CO 2 emissions in 2010 tipped the scales at 26.8 billion tons (USGS)

So, the Natural Drivers: Astronomical Factors (Milankovitch Cycles) Solar Output and Volcanism Do not account for the recent rapid warming

Instead, Greenhouse Gases account for the warming over the past 50 years. They result from the combustion of Fossil Fuels (coal, oil, natural gas) Agriculture (cows) Deforestation Melting Permafrost…

NASA Atmospheric Infrared Sounder (AIRS) July 2008 Global Carbon Dioxide Levels

Dendroclimatology Tree rings provide records of climate history. Insight into past climates is based on information in geological and biological records. What evidence do we have?

Palynology provides information of past vegetation, and therefore, climate. Lake bottom sediment cores trap pollen grains

Oxygen Isotope Analysis Ratio of Oxygen-18 to Oxygen-16 in calcite from deep sea sediment cores measured with a mass spectrometer reveal climate 500 million years ago.

Less Oxygen 18 = colder climatic periods

CO 2 has risen every year since measurements began

According to the Environmental Protection Agency, greenhouse gases from fossil fuel combustion are responsible for most of the warming of the last 50 years.

Earth’s mean surface temperature has increased about 1.5ºF since 1900 NOAA’s State of the Climate Report NASA’s Surface Temperature Analysis NASA reports that most of the warming has occurred over the past 30 years.

2005 and 2010 tied as the hottest years on record to 2010 is the hottest decade on record to 2000 is the second hottest decade on record was the hottest year on record in the U.S.

Climate models predict that mean Earth temperature could increase from 2.5 ºF to 10.5ºF above 1990 levels by “Global temperatures are dangerously close to the highest ever estimated to have occurred in the past million years” (NASA)

Since 1950, the Arctic has lost 50% of its extent

The first report of the IPCC was published 1990, then 1995, 2001, & the FAR (AR4) in 2007 Climate Change 2007: The Physical Science Basis Climate Change 2007: Impacts, Adaptation and Vulnerability Climate Change 2007: Mitigation of Climate Change Climate Change 2007: Synthesis Report